1. Technical Field
The present invention relates generally to computer networking devices and more particularly to a packet arrival time detector for use in a Home Phoneline Network Alliance (HPNA) receiver.
2. Description of the Background Art
Digital communication systems over a shared medium transmit information organized into discrete packets. To recover the information, a receiver must be able to determine when packets arrive, and to distinguish packets from noise. In general, the receiver must determine a Packet Arrival Time (PAT) for each received packet, since the packets might be transmitted from different asynchronous sources. The PAT is commonly used by sections of the receiver to prepare for the onset of the information-bearing portion of the packet. For example, an equalizer can use the PAT as an indicator of when to start training. In this situation, the more accurate the PAT, the faster the equalizer will converge before the onset of information, which makes the receiver less prone to packet errors.
A receiver typically detects the arrival time of signals, such as packets, using a correlator. Correlators compare, or correlate, a received signal with a known signal stored at the receiver. Among other things, correlators multiply samples of a received signal with samples of a known signal and then sum the products. Correlators commonly receive complex signals including real and imaginary components, and thus require many multipliers to perform correlations. Multipliers are typically costly components due to their large space and power requirements. Thus there exists a need for an economical and efficient packet arrival time detector.